使用jackson来进行数组格式的json字符串转换成List。

有一个字符串如下。如下，也是通过jackson把list转换成的json字符串，我想把它转过来，看网上的内容都不尽人如意，都是片断的内容。估计只有写的知道怎么使用，所以就直接看了jackson的官网，知道了使用方法。

用的类主要是

import org.codehaus.jackson.type.TypeReference;
import org.codehaus.jackson.map.ObjectMapper;

要转的字符串如下：

[{"id":"36CD0224C1ED25F5E0538A3B0B7A8190","catgId":null,"matcAmont":50000,"lendPoolId":"36CD0224C1C225F5E0538A3B0B7A8190","balance":50000,"matchFlag":1,"isLock":1,"createTime":1467576000000,"userId":0,"mltCustLendPool":{"id":"36CD0224C1C225F5E0538A3B0B7A8190","userId":157020,"state":1,"isLock":1,"balance":50000,"curTotaAmt":50000,"syncDate":1467561600000,"inviFlag":2,"investTime":1467595065000,"deadline":1499131065000,"billDate":1467681465000,"billDay":5,"productId":"6","productName":"xxx","investAmt":50000,"prodOrderId":38662,"userTelephone":"15922166933","userName":"张三","idcardNum":"1111111111111","projectNum":null,"matchModelCode":null,"creditProduct":{"id":"290AA19B1134838EE053A716C0769130","swldid":"6","prodName":"xxx","prodType":null,"prodRate":0.13,"synFeeRate":null,"payCapitalType":null,"freezeTime":12,"prodCode":6,"prodCatgory":1,"unit":1},"subject":null},"orderFlag":null,"subject":0,"projectNum":null,"matchModeCode":"1"},{"id":"36DA5B50E54E2790E0538A3B0B7A2261","catgId":null,"matcAmont":50000,"lendPoolId":"36CD0224C1C225F5E0538A3B0B7A8190","balance":50000,"matchFlag":1,"isLock":1,"createTime":1467748800000,"userId":0,"mltCustLendPool":{"id":"36CD0224C1C225F5E0538A3B0B7A8190","userId":157020,"state":1,"isLock":1,"balance":50000,"curTotaAmt":50000,"syncDate":1467561600000,"inviFlag":2,"investTime":1467595065000,"deadline":1499131065000,"billDate":1467681465000,"billDay":5,"productId":"6","productName":"xxx","investAmt":50000,"prodOrderId":38662,"userTelephone":"15922166933","userName":"王dd","idcardNum":"2222222222222","projectNum":null,"matchModelCode":null,"creditProduct":{"id":"290AA19B1134838EE053A716C0769130","swldid":"6","prodName":"dfdfd","prodType":null,"prodRate":0.13,"synFeeRate":null,"payCapitalType":null,"freezeTime":12,"prodCode":6,"prodCatgory":1,"unit":1},"subject":null},"orderFlag":null,"subject":0,"projectNum":null,"matchModeCode":"1"}]

主要代码如下：

        ObjectMapper mapper = new ObjectMapper();
        List<MltWaitLendReco> lendReco = mapper.readValue(listStr,new TypeReference<List<MltWaitLendReco>>() { });
        System.out.println(lendReco.get(0).getId());

这样就可以把json字符串转换成想要的List.

注意readValue()方法里的new TypeReference<List<MltWaitLendReco>>() { }写法很关键，你写成List.class是不行的，

还有一点，ObjectMapper类在com.fasterxml.jackson开头的包里也有，这里用的是org.codehaus.jackson

这里还有一个以前用的，对象和Json互转的工具类

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

public class JsonUtils {

    /**
     * Logger for this class
     */
    private static final Logger logger = LoggerFactory.getLogger(JsonUtils.class);

    private final static ObjectMapper objectMapper = new ObjectMapper();

    static {
        objectMapper.configure(JsonParser.Feature.ALLOW_COMMENTS, true);
        objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
        objectMapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
        objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_CONTROL_CHARS, true);
        objectMapper.configure(JsonParser.Feature.INTERN_FIELD_NAMES, true);
        objectMapper.configure(JsonParser.Feature.CANONICALIZE_FIELD_NAMES, true);
        objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }

    public static String encode(Object obj) {
        try {
            return objectMapper.writeValueAsString(obj);
        } catch (JsonGenerationException e) {
            logger.error("encode(Object)", e); //$NON-NLS-1$
        } catch (JsonMappingException e) {
            logger.error("encode(Object)", e); //$NON-NLS-1$
        } catch (IOException e) {
            logger.error("encode(Object)", e); //$NON-NLS-1$
        }
        return null;
    }

    /**
     * 将json string反序列化成对象
     *
     * @param json
     * @param valueType
     * @return
     */
    public static <T> T decode(String json, Class<T> valueType) {
        try {
            return objectMapper.readValue(json, valueType);
        } catch (JsonParseException e) {
            logger.error("decode(String, Class<T>)", e);
        } catch (JsonMappingException e) {
            logger.error("decode(String, Class<T>)", e);
        } catch (IOException e) {
            logger.error("decode(String, Class<T>)", e);
        }
        return null;
    }

    /**
     * 将json array反序列化为对象
     *
     * @param json
     * @param jsonTypeReference
     * @return
     */
    public static <T> T decode(String json, TypeReference<T> jsonTypeReference) {
        try {
            return (T) objectMapper.readValue(json, jsonTypeReference);
        } catch (JsonParseException e) {
            logger.error("decode(String, JsonTypeReference<T>)", e);
        } catch (JsonMappingException e) {
            logger.error("decode(String, JsonTypeReference<T>)", e);
        } catch (IOException e) {
            logger.error("decode(String, JsonTypeReference<T>)", e);
        }
        return null;
    }
}

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